1998 Explorer heater controls not working

[vetski179]

Recently, the controls stopped working. Keeps cranking low heat regardless of where the controls are positioned. Cycling the controls does not help. Any ideas? Thank you. BTW, 1998 Explorer 5.0 w 70k miles.

 

[Electrohacker01]

Pure guess, but could it be vacuum? I'm pretty sure the blend door (which selects heat vs cold) uses vacuum

 

[J_C]

You wrote controlS, do you have EATC (auto climate control) or manual? I am unfamiliar with the adjustments for EATC.

On either my first suspicion would be the blend door actuator. I assume you still have different fan speeds working and the A/C compressor is cycling on when set to cold?

 

[vetski179]

The heater controls are the standard controls, i.e. cold to warm rotatable control knob, not the EATC (I'm guessing the EATC is where you set a temperature). When cycling the a/c to the 'on' position, you can hear the compressor turn on. So, everything seems to be working as normal except the temperature control. I heard a vacuum hiss when cycling the right knob, so I'll pull the heater control panel and check for a vacuum issue.

 

[J_C]

As far as I know, the vac lines determine where the air comes out (and in), but the electrically powered Blend Door Actuator determines the hot/cold mix.

Member GTMountain recently posted a diagram that could be useful:

 

[vetski179]

Did some tests: Removed blend door actuator and cycled temperature control knob. It is working. While glove box was out of the way, checked the vacuum door that opens when you go from regular a/c to max a/c. That works. The problem seems to be this: When the heater control is on a/c, it blows hot. Rotating the temperature knob makes no difference. Turning to max a/c seems to return the temperature control to normal functionality, however, not very cold, even when the temp knob is rotated to full cold.

 

[vetski179]

In my continuing diagnosis of the problem today, I think I found the issue: a broken blend door. With the actuator out of the way, I stuck a mirror up where actuator would be, at an angle, so I could see down where the actuator shaft goes into the axle that controls the door. Looks broken to me.

 

[vetski179]

Ordered a Dorman 902-221. Will let you know how installation goes. Thanks for all the help.

 

[Spuddy]

It looks like your blend door 'shaft' is not completely broken, and it has only cracked a piece off the D-shaft-hole. Sadly, that means trouble and you're likely going to have the same problem I did: after cutting the access flap, the door still doesn't want to come out, because too much of the shaft is still intact, and still seated in its sockets.

So, when you cut your flap to access the blend door you will need to include cutting past the blend door shaft socket as well. And, if it breaks - like mine did - you're going to have a hard time trying to make your adhesive, the blend door itself, the socket and flap all defy gravity while the adhesive sets up.

I would not use the Dremel tool for this job again, because it removed too much material and made reassembly quite a pita.

May good luck be with you...

 

[vetski179]

The hardest part of the job was propping myself up in a position to work under the passenger side dash! Hurtin' a bit today! So, I did as Spuddy suggested and cut further than the instructions said and cut the bottom shaft socket out too. The busted door fell right out, and there was plenty of tape with the kit to put the cut out piece (lower pivot socket included) to secure it back in place. In hindsight, I might've been able to do it without cutting out the socket. Problem is, it seemed to me you had to make the cutting decision beforehand, because deciding to cut the socket out by itself AFTER making the initial pie shaped cut, as the directions show, would make taping in the socket by itself tough.

Cut out piece ready for reinstallation.

The finished product. Not pretty, but it works! Plus, I, nor anyone else I know, have eyes in our feet!

 

[vetski179]

Thank you to all for your replies. Hope my experience will help someone.

 

[Spuddy]

In hindsight, I might've been able to do it without cutting out the socket... Problem is, it seemed to me you had to make the cutting decision beforehand, because deciding to cut the socket out by itself AFTER making the initial pie shaped cut, as the directions show, would make taping in the socket by itself tough.

Yeah, that's what happened to me, and what was just about to happen to you as well...

For me and you, it was not a decision but a necessity. When the top splits (mine failure looks almost identical - imagine that), if the socket remains attached to the plenum, the unbroken half of of the shaft from coming out of the upper socket and the door will not come out.

And, yes, then you have to cut the bottom socket out, and now the angles get really wonky while trying to put 'er back together.

Congratulations are in order...